<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    table {
      border-collapse: collapse;
    }

    td {
      border: 1px solid #000;
      padding: 8px 12px;
    }
  </style>
</head>
<body>
  
  <table>
    <tr>
      <td>1-1</td>
      <td>2-1</td>
      <td>3-1</td>
      <td>4-1</td>
    </tr>
    <tr>
      <td>1-2</td>
      <td>2-2</td>
      <td>3-2</td>
      <td>4-2</td>
    </tr>
    <tr>
      <td>1-3</td>
      <td>2-3</td>
      <td>3-3</td>
      <td>4-3</td>
    </tr>
    <tr>
      <td>1-4</td>
      <td>2-4</td>
      <td>3-4</td>
      <td>4-4</td>
    </tr>
  </table>

  <script>

    var tableEl = document.body.firstElementChild

    // // 1.获取1-1
    // var row1El = tableEl.rows[0]
    // var cell1El = row1El.cells[0]
    // console.log(cell1El)

    // // 2.获取2-2
    // var row2El = tableEl.rows[1]
    // var cell2El = row1El.cells[1]

    // for循环
    for (var i = 0; i < tableEl.rows.length; i++) {
      var rowEl = tableEl.rows[i]
      var cellEl = rowEl.cells[i]

      // 设置样式
      cellEl.style.backgroundColor = "red"
      cellEl.style.color = "white"
    }

  </script>

</body>
</html>